The present invention relates to the preparation of very strong solid acids and to processes for hydrocarbon conversion reactions employing such very strong solid acids as catalysts.
The strongest acid solutions known are combinations of Bronsted and Lewis acids such as hydrogen flouride (HF) and antimony pentaflouride (SbF.sub.5). These "superacids" are highly active catalysts for hydrocarbon reactions proceeding through carbonium ion intermediates, but they have the processing disadvantages of being corrosive and difficult to separate from reaction products.
U.S. Pats. No. 3,855,342, 3,855,343, 3,862,258, and 3,879,489 describe processes for preparing and applying hydrocarbon alkylation catalyts from macroporous sulfonic acid ion-exchange resins such as Amberlyst 15 and a Lewis acid, boron triflouride (BF.sub.3). These catalysts have the disadvantage of requiring a constant recycle of boron triflouride, a gas at ambient conditions, which is noxious and difficult to handle safely. They have the further disadvantage of requiring addition of hydrogen fluoride for activity maintenance, and this compound is also noxious and difficult to handle safely.
U.S. Pat. No. 3,975,299 describes processes for preparing hydrocarbon alkylation, isomerization, and/or cracking catalysts from sulfonated or fluorided aluminum oxide and a Lewis acid, antimony pentafluoride. These catalysts have the disadvantage of requiring antimony pentafluoride, a chemical which is expensive, corrosive, noxious, and difficult to handle. They have the further disadvantage of requiring addition of hydrogen fluoride to compensate for any hydrogen fluoride lost from the catalyst during operation.
It is the object of the present invention to prepare a solid catalyst having superacid properties -- analogous to those of the solution catalysts -- but lacking the processing disadvantages attributed to such solution catalysts. It is the further objective of present invention to prepare a solid catalyst having these superacid properties and not containing any fluorine, a component which generally leads to processing problems related to handling and safety.